This invention relates to apparatus for filtering a gas stream and in particular to an apparatus for releasably securing a filter element to the tube sheet of a dust collector of the type used for separating particulate material from a gas stream.
Prior to the present invention, various types of fabric filters or bag houses have been known. Typically, fabric filters of the type to which the present invention relates include a filter element mounted on a tube sheet inside the dirty gas compartment of the filter housing. Gas to be filtered enters the dirty gas chamber, for passage through the filter element and through an opening in the tube sheet to the clean gas chamber. Clean gas exits the apparatus to atmosphere. Particulate material contained within the dirty gas stream is collected on the outside surface of the filter element. There are various techniques for removing the particulate material from the surface of the filter element including a shaker system for gently shaking the filter bag and a reverse air cleaning system which includes means for supplying clean air to the inside of the filter element for reverse flow through the filter element. A further technique is to supply a pulse of high pressure air into the filter element which both shakes and causes a reverse air flow. Typically, the particulate material drops into a hopper from which it is discharged to disposal.
Also prior to the present invention it was known to utilize cartridge type filters for carrying out the filtering process. An example of such a cartridge filtering apparatus is shown in U.S. Pat. No. 4,218,227 issued Aug. 19, 1980. These may include a folded paper or fabric which is supported by a cage or screen apparatus.
An important element of a dust collector is the manner in which the filter element is mounted within the dust collector in general. Often, the filter element is secured by some means to the tube sheet. The apparatus utilized must be able to adequately secure the filter element to the tube sheet inside the dirty gas chamber while maintaining a seal between the filter element and the tube sheet. Since it is necessary to periodically change the filter element, the means for securing the filter element to the tube sheet must be capable of easily releasing the filter element from the tube sheet to provide easy maintenance.
Various techniques for securing filter elements to tube sheets of a dust collector are shown, for example, in U.S. Pat. Nos. 4,257,790, 3,508,383, 3,618,300, 3,538,687 and 3,097,410. U.S. Pat. No. 4,292,061 discloses an air filter assembly using a clamping band and latch mechanism in a different field of use as compared with the present invention.
Prior to the present invention, cartridge filters were typically secured within a dust collector by having a rod pass longitudinally through the filter element with the rod secured to the tube sheet as by bolting.